The present invention relates to multi-chip-modules, in which a plurality of microwave/millimeterwave integrated circuits (hereinafter referred to as MICs) utilizing electromagnetic waves in the micro-band to milli-band are mounted in a package substrate.
In a prior art multi-chip-module with a plurality of MICs mounted therein, a microwave/millimeterwave transceiving circuit is constructed such that elementary circuits such as amplifiers and oscillators or composite circuits such as ones in which a multiplier and an amplifier are made integral, ones in which a mixer and an amplifier are made integral, and ones in which a transmitting unit or a receiving unit are made integral, are interconnected by metal waveguide circuits or three-dimensional circuits.
Particularly, in a multi-chip-module, a low temperature simultaneous baking substrate such as glass ceramic substrate is used as dielectric substrate, is as low as 3 W/mxc2x7K of heat conductivity. To cope with this, a multi-chip-module having heat radiation via holes for promoting heat radiation, is proposed in, K. Ikuina et. al., xe2x80x9cGlass-Ceramic Multi-chip-module for Satellite Microwave Communication Systemxe2x80x9d, Proc. ICEMCM ""95, 1995, pp. 483-488.
However, even in the multi-chip-module proposed in the above treatise, the thermal conductivity is at most several W/mxc2x7K, and it is impossible to greatly improve the heat radiation efficiency. Accordingly, a structure in which metal is applied or buried for permitting heat dissipation from a semiconductor chip is provided as a means for improving the heat radiation efficiency.
In the above treatise is also proposed a multi-chip-module having a structure that lids serving as shielding members for shielding high frequency circuits and functional elements from one another are each bonded to a pack,age substrate for each function element constituted by a monolithic MIC such as an oscillator, a mixer, an amplifier and a transceiver.
Heretofore, a ceramic package of the multi-chip-module is connected to a printed circuit board as a mounting substrate by forming solder balls on an electrode pad provided on the ceramic package and connecting the ceramic package via the solder ball to the printed circuit board. This method of connection is called BGA (Ball Grid Array) connection. As another connecting means, the ceramic package is mounted on the printed circuit board by soldering LCC (Leadless Chip Carrier) electrodes provided on the ceramic package to the printed circuit board.
However, in the multi-chip-module, in which the microwave/millimeterwave transceiving circuit is such that elementary circuits and composite circuits are interconnected by metal waveguide circuits and three-dimensional circuits, a drawback occurs in that the metal waveguides is complicated in shape and also such steps as screwing and welding are required for the waveguide formation. This is undesirable from the standpoint of reducing the cost of the multi-chip-module.
In the multi-chip-module, in which metal is applied or buried for dispersing heat from the semiconductor chip, the metal has a thickness of at least 0.2 to 0.5 mm in view of the limit of the processing accuracy, and discontinuity of high frequency grounding surface is produced, thus deteriorating the high frequency characteristics.
In the multi-chip-module, in which lids are each bonded for each function element for electromagnetic shielding and hermetical sealing of function elements from one another, a plurality of lids should be bonded to the package substrate and hermetically sealed. In this bonding step, the yield value of the hermetical sealing is the accumulation of the yield value of the hermetical sealing of one lid by the number of lids mounted on the package substrate, and is therefore very low. In addition, when defective sealing is detected in the bonded part of either one of the lids as a result of a leak test conducted on the completed multi-chip module, it is difficult to determine which one of the lids has the defectively sealed bonded part because of the multiple lid structure of this multi-chip-module.
Furthermore, in the prior art structure, in which the ceramic package of the multi-chip-module is soldered to the printed circuit board, the low linear thermal expansion coefficient of the ceramic substrate, for instance of aluminum nitride, which measures 3.5 to 4.5 ppm/xc2x0 C., gives rise to the following problem in the connection. When the connection is made by using solder with a linear thermal expansion coefficient of 13 to 16 ppm/xc2x0 C. (for instance xe2x80x9cFR-4xe2x80x9d, manufactured by Mitsubishi Gas Chemical Co., Ltd.), cracks or fissures are generated in solder bonded parts by working ambient temperature changes, as described in, Yoji Kanuma, xe2x80x9cEfficient Way and Actual Practice of Reliability Acceleration Testsxe2x80x9d, pp. 161-165 published on Oct. 4, 1997. Therefore, it has been impossible to realize a package size larger than 20 mm on one side.
An object of the present invention is to provide a microwave integrated circuit multi-chip-module, which permits simplification of the step of bonding the shielding member and improving the yield of the hermetical shielding on the bonded part of the shielding member.
Another object of the present invention is to provide a microwave integrated circuit multi-chip-module mounting structure, in which portions connected to the mounting substrate are not readily broken apart by heat generation in the microwave integrated circuit multi-chip-module.
According to an aspect of the present invention, there is provided a microwave integrated circuit multi-chip-module comprising a package substrate having a high frequency transmission line formed on the surface, a plurality of microwave integrated circuits mounted thereon, and a shielding member bonded to the surface of the package substrate and electromagnetically shielding the high frequency transmission line and each microwave integrated circuit from each other, wherein the shielding member has recesses formed such as to face the high frequency transmission line and the microwave integrated circuits and shielding wall portions partitioning the recesses from one another.
In this structure, the high frequency transmission line and each microwave integrated circuit of the microwave integrated circuit multi-chip-module are electromagnetically shielded by a single shielding member,. Thus, the bonding of the shielding member to the package substrate is completed in a single step, thus simplifying the shielding member boding process.
The surface of the package substrate and the outer periphery of the shielding member are hermetically shielded from each other by fillets made of a water-resistant material or a solder. Thus, the yield of the hermetical shielding on the bonded part of the shielding member is improved.
The package substrate has a tubular waveguide part for guiding electromagnetic waves inputted to or outputted from the high frequency transmission line. The waveguide part has a plurality of via holes formed in a predetermined interval in a tubular fashion in the package substrate.
According to another aspect of the present invention, there is provided a mounting structure for mounting a microwave integrated circuit multi-chip-module comprising the microwave integrated circuit multi-chip-module described above, and a mounting substrate with the microwave integrated circuit multi-chip-module mounted therein, wherein the side surfaces of the package module of the microwave integrated circuit module has external connection electrodes connected to the microwave integrated circuits, and the mounting substrate has a receptacle member with the microwave integrated circuit multi-chip-module mounted therein and having flexible connector terminals connected to the external connection electrodes of the microwave integrated circuit multi-chip-module.
In this structure, even when the microwave integrated circuit multi-chip-module expanding due to heat generation in the microwave integrated circuits, the expansion is absorbed by flexing deformation of the connector electrodes, thus improving the reliability of the connection between the microwave integrated circuit multi-chip-module and the mounting substrate.
At least a portion of parts of the mounting substrate and the receptacle member that face the microwave integrated circuit multi-chip-module when the, microwave integrated circuit multi-chip-module is mounted in the receptacle member, has an opening, a projection formed in a support member with the microwave integrated circuit multi-chip-module mounted therein being inserted through the opening. Thus the heat generated in the MMICs is conducted through the projection of the support member to the outside.
According to another aspect of the present invention, there is provided a microwave integrated circuit multi-chip-module comprising a package substrate of a high temperature co-fired ceramic of a dielectric property including a plurality of high frequency circuit portions formed on the surface, and a shielding member of a non-magnetic metal having a plurality of recesses formed in positions corresponding to the respective high frequency circuit portions, the package substrate and the shielding member being bonded for electromagnetically shielding the high frequency circuit portions.
The shielding member is of tungsten and the package, substrate is beryllia or nitride. The package substrate is made of aluminum nitride, beryllia or silicon nitride. The package substrate and the shielding member are bonded together by a conductive adhesive or a solder. The surface of the package substrate and edge of the shielding member are hermetically sealed to one another by fillets of moisture-resistant resin or a solder.
According to still another aspect of the present invention, there is provided a mounting structure for mounting a microwave integrated circuit multi-chip-module comprising a package substrate of a high temperature co-fired ceramic of a dielectric property including a plurality of high frequency circuit portions formed on the surface, a shielding member of a non-magnetic metal having plurality of recesses formed in position corresponding to the respective high frequency circuit portions, the package substrate and a plurality of leadless chip carrier electrodes, the shielding member being bonded for electromagnetically shielding the high frequency circuit portions; and a receptacle having a plurality of flexible connector electrodes each connected to the corresponding leadless chip carrier electrode.
The leadless electrodes are mounted by a solder re-flow on a printed circuit board serving as a mounting board. The leadless electrodes are mounted by a solder re-flow on a printed circuit board as a mounting board and the printed circuit board is secured by a mother board as a support member of a metal. The leadless electrodes is mounted by a solder re-flow on a printed circuit board as a mounting board, the printed circuit board is secured a mother board as a support member of a metal, and the projection of the mother board has a rectangular hole facing rectangular cavity formed in the multi-chip-module functioning as part of the tubular waveguide. The package substrate is made of aluminum nitride, beryllia or silicon nitride. A buffer plate is inserted between the package substrate and the high frequency circuit portion in order to reduce the mechanical stress caused to the high frequency circuit portion due to the difference of the temperature expansion coefficients.
Other objects and features will be clarified from the following description with reference to attached drawings.